Neural Basis of Theory of Mind in Children and Adults with Delayed Access to Language

Humans use language to describe and communicate about the minds of others. Indeed, behavioral studies have provided evidence that language is necessary for typical “theory of mind” (ToM) development in childhood. Maternal use of mental state vocabulary predicts early ToM development in hearing children (Ruffman et al., 2002) and children who are Deaf (Moeller & Schick, 2006). Deaf children born to non-signing households have delayed theory of mind development (e.g. Peterson & Siegel, 1999), whereas Deaf children born to signing households do not (e.g. deVilliers, 2005). The current project uses fMRI to investigate the development of brain regions recruited for ToM reasoning in children and adults who are Deaf and born into non-signing versus signing households. Studying these populations provides insight into whether delayed access to language affects the neural basis of theory of mind. First, using nonverbal and verbal ToM behavioral batteries, we replicate previous evidence suggesting that behavioral ToM delays are specific to verbal tasks, and present only in Deaf children with delayed access to language. Second, using a naturalistic viewing task previously shown to drive responses in ToM brain regions, we find evidence for similar responses in these regions despite delayed access to language. Together, this evidence complements previous behavioral studies, and suggests that the neural basis of ToM in individuals with delayed access to language is indistinguishable from control groups by middle childhood.